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Sunday, March 31, 2013

Aviation Week and Space Technology reports that the President’s next budget request for NASA will include funds to
begin developing a mission to bring an asteroid to the Earth-moon system. The initial goal will be to provide a
destination for a manned mission to an asteroid, but if the idea works, it
could kick start asteroid mining.

The insight behind the mission is that it’s technically easier and
cheaper to bring a small asteroid to where it can easily be reached by a manned
mission than it is to send astronauts to an asteroid. This may seem counter-intuitive. The feasibility study that proposed the idea
defined a small asteroid as around 7 meters in diameter with a mass of 250,000
to 1,000,000 kg. The robotic spacecraft
will have to travel to the asteroid, match its spin, net it, de-spin it, and
then drag it back to the Earth-moon system.
However, robotic spacecraft and asteroids don’t require complex life
support systems and near fail safe engineering systems. If the robotic mission fails, it’s a
shame. If a human mission fails with the
loss of the astronauts, it’s a catastrophe.

This concept was originally proposed last year in a study carried out
by the Keck Institute for Space Studies at the California Institute for
Technology (which is also home to the Jet Propulsion Laboratory). The study participants included scientists
and engineers from a wide range of institutions. You can read the report here.

The mission would be enabled by three key developments. First, we need the technology to be able to
find a number of very small asteroids so that one can be selected with the
optimum trajectory, size, and spin. (An
asteroid spinning too fast would exceed a spacecraft’s capacity to de-spin
it.) The desired C-type of asteroids
would be dark and spotting them is considered by at least one of the authors of
the feasibility study as the toughest part of the concept. The size of the target asteroid was selected
as the smallest that was believed to be detectable in large enough numbers to
find a good candidate.

Second, high powered solar electric engines would be needed to be able
to transport the asteroid back to the Earth-moon system. The spacecraft will need to simultaneously operate
four 10-kW engines to enable the mission.
For comparison, the total power system for the Dawn spacecraft, which
also uses ion propulsion, is 10-kW.
Bringing the asteroid to the vicinity of the moon puts it near the top
of the Earth-moon system’s gravity well and greatly diminishes the propulsion
requirements for the mission compared to bringing the asteroid to lower Earth
orbit. A near lunar destination also
minimizes the risk of impact with the Earth (it’s impolite, to say the least,
to drop a small asteroid in someone’s back yard, although a C-type asteroid
would likely disintegrate before reaching the Earth’s surface).

The final key development will be the launch system and spacecraft
needed to deliver astronauts to the asteroid.
NASA already is working on these – the Space Launch System and Orion
spacecraft. What it has lacked has been
a credible use for the system. Flights
to near Earth asteroids require months or years to a destination that lacks
drama, lunar missions require landers that aren’t funded, and Mars is a distant
dream. What the proposers of this scheme
– and now NASA, apparently – believe is that a relatively short flight to an
asteroid brought to our backyard would be a winning combination.

Once an asteroid is returned, what would the astronauts do? The proposers suggest that early missions
would be focused on scientific examination, testing operations near and on a
tiny body, and validation of methods that eventually could lead to mining and
processing the asteroid’s material. C-type
asteroids are rich in volatiles and conveniently have the consistency of dried
mud, simplifying mining. A 7 m carbonaceous
asteroid is estimated to contain 100 tons of water, a similar amount of
carbon-rich compounds, and 90 tons of metals (mostly iron). A key problem with enabling human exploration
beyond the moon is the cost of delivering fuel and water beyond low Earth
orbit. One or more small asteroids could
become fueling stations for missions two or three decades from now.

The cost to deliver the asteroid to the vicinity of the moon was
estimated at $2.65 billion, or somewhat more than the cost of the Curiosity
Mars rover mission. The human
spaceflight system is being paid for separately. The proposers do not give a cost estimate for
developing and operating the mining equipment.
For the coming year, NASA reportedly will ask to $100M to refine the
technical requirements of the asteroid capture spacecraft and operations. A launch to an asteroid presumably would not
occur until the end of this decade or early in the next.

Editorial thoughts: As a scientific mission, I don’t know how the
science community would rank an asteroid retrieval. For the same price as the $2.65B cost
estimate, NASA could fly a Europa mission, conduct sample returns from several
types of asteroids, cover much of the cost of a Mars sample return, or fly an
orbiter and probe to Uranus. (In reading
the proposer’s report, it appears that the technical analysis of the mission is
in the early stages. I would not be
surprised to see the final cost of the mission be substantially more than the
current estimate.)

However, if humanity is to move into deep space, then this mission, I
believe, could a brilliant interim step.
It would provide a target for sustained operation at the cusp of deep
space, much as the early Gemini missions tested the technology and operations that
led to the success of the Apollo mission.
The asteroids brought back could also provide the raw materials needed
to enable missions deeper into the solar system. (Bringing back other types of asteroids could
also provide more valuable metals that might be mined for return to
Earth.)

At the moment, political leaders have not been willing to fund bold
initiatives for human spaceflight. Perhaps
the greatest value of this mission would be that it would enable forward
momentum so that future politicians can make the bold choice.

Monday, March 18, 2013

At the end of March, planetary scientists will gather for the 44th
Lunar and Planetary Science Conference.This is one of the top scientific conferences held every year for
planetary science, with thousands of oral presentations and posters presenting
the latest results from on on-going missions or analyzing data from past
missions.(A good source for the
meeting’s highlights will be the Planetary Society’s blog.)

A tiny fraction of the presentations at LPSC will deal with future
missions.However, this is still one of
the best sources for insights into details of missions under development. In this post, I’ll cover some of the
abstracts for the presentations that give a flavor of the breadth of the proposals.(Abstracts are typically two pages and
qualify as mini papers, so there’s plenty of detail.The abstracts are also published on the web
well ahead of the meeting, so I was able to write this post prior to the
meeting.)

Narrowing down the abstracts proved to be hard.There are abstracts that provide the first
detailed descriptions I’ve seen of the instruments that will fly on future
missions.Examples in this category include
the cameras and visible to near-infrared spectrometer for NASA’s upcoming
OSIRIS-Rex asteroid mission (launch in 2016).In some cases, I’ve already written about the proposed missions or very
similar versions, such as the European Inspire concept for multiple geophysical
stations on Mars, landers for Venus, or flyby spacecraft for Jupiter’s moon Io.

What follows are summaries of my selection of abstracts that present
concepts new to this blog and that I found most interesting.

At the end of March, planetary scientists will gather for the 44th
Lunar and Planetary Science Conference.This is one of the top scientific conferences held every year for
planetary science, with thousands of oral presentations and posters presenting
the latest results from on on-going missions or analyzing data from past
missions.(A good source for the
meeting’s highlights will be the Planetary Society’s blog.)

A tiny fraction of the presentations at LPSC will deal with future
missions.However, this is still one of
the best sources for insights into details of missions under development. In this post, I’ll cover some of the
abstracts for the presentations that give a flavor of the breadth of the proposals.(Abstracts are typically two pages and
qualify as mini papers, so there’s plenty of detail.The abstracts are also published on the web
well ahead of the meeting, so I was able to write this post prior to the
meeting.)

Narrowing down the abstracts proved to be hard.There are abstracts that provide the first
detailed descriptions I’ve seen of the instruments that will fly on future
missions.Examples in this category include
the cameras and visible to near-infrared spectrometer for NASA’s upcoming
OSIRIS-Rex asteroid mission (launch in 2016).In some cases, I’ve already written about the proposed missions or very
similar versions, such as the European Inspire concept for multiple geophysical
stations on Mars, landers for Venus, or flyby spacecraft for Jupiter’s moon Io.

What follows are summaries of my selection of abstracts that present
concepts new to this blog and that I found most interesting.

Abstract 1838: SELENE-2 – The Japanese space agency has been studying a
follow on mission to their highly successful SELENE lunar orbiter since
2009.SELENE-2 would place a lander and
rover on the lunar surface, and would be Japan’s first major lander on another
world.(The Hayabusa missions include
tiny landers for asteroids.)In addition
to developing the lander and rover technology, the mission would conduct serious
science.The lander would be a
geophysical station with a seismometer, a heat flow probe, a magnetometer,
precise radio tracking, and a laser reflector.(The last would allow precise measurements of the distance between the
Earth and lunar surfaces by reflecting laser pulses from Earth-bound
telescopes.Combined with radio
tracking, this will help study tiny wobbles in the moon’s position giving clues
to the interior structure.)The rover
would study the chemistry of the lunar surface with a number of spectrometers
to study composition.An orbiter with a
small number of instruments would complete the mission.Unfortunately, it appears from the abstract
that the Japanese space agency has lacked funds to move the mission out of the
study phase and into development.As a
result, the launch date has slipped from 2015 to 2018 at the earliest.If this mission does fly, it will join a number
of others from China, Russia, and India in the coming decade.The moon could prove to be even more crowded
with spacecraft than Mars will be.

The following two abstracts propose missions for very small spacecraft,
built on the CubeSat paradigm.CubeSats are
designed around small, standard building blocks (cubes).Depending on the mission, a spacecraft may
use one or several cube building blocks.CubeSats have become popular for Earth orbital missions for implementing
very focused science on small budgets.Various teams are now looking at potential uses of CubeSats for
planetary missions.Many instruments
cannot be hosted on these tiny platforms, so these craft won’t replace larger
spacecraft.However, CubeSats may enable
a new class of standalone missions or as auxiliary spacecraft carried by much
more capable mother ships.

Abstract 1233: LunarCube – This abstract highlights the challenges of
adapting CubeSats to missions beyond the Earth and the limitations on the
science they can do.The authors point
out that advances in consumer electronics have led to reductions in size, mass,
and power while processing capabilities have increased.However, to operate beyond Earth orbit,
CubeSats must be enhanced for longer mission lives, require navigation and
propulsion systems, more robust communications systems, and hardening for more
severe radiation and thermal environments.(These are the reasons that planetary missions of all sizes cost
substantially more than equivalent Earth observing satellites.)Once these challenges are met, the resources
for the instrument(s) will be constrained.A Lunar Water Distribution LunarCube could carry a near infrared
spectrometer to map water in lunar soils that would be limited to 2 kilograms,
2 Watts of power, and 1500 bytes of data returned per day.Two other mission concepts are listed with
similarly constrained payloads: a craft to analyze plumes kicked off the lunar
surface by a separate impact craft and a proof of concept radio astronomy
mission that would operate from the surface.The ultimate goal for the LunarCube project is to create a design for a
“virtual ‘smart phone’ with a variety of experiments.”Editorial Thoughts: Despite the limitations,
missions like these to the moon or perhaps to near Earth asteroids would
perform real science.They would be
especially useful for training new researchers on how to develop and manage
missions at relatively low cost.

Concept for small Uranus spacecraft based on CubeSat form factor.From LSPC 2013 Abstract 1860

Abstract 1860: Small Spacecraft Exploration of Uranian Moons – This
abstract proposes a solution for an eventual Flagship (~$2B) Uranus
orbiter.To fully observe Uranus and its
magnetosphere, the spacecraft will need an orbit that carries it over Uranus’
poles.The moons, however, orbit above
the equator and will be difficult to observe.The authors of this abstract propose that the main spacecraft would
carry four large CubeSat-based daughter spacecraft that would examine the
moons.(CubeSats designs can be enlarged
by ‘stacking’ multiple cubes; this design would have the volume of six
cubes.)These small spacecraft would
operate in pairs.As a pair approaches a
moon, they would image its surface and measure its gravity by monitoring each
other’s relative speed (much as the two GRAIL spacecraft did for our
moon).These craft would need advanced
technologies.Their solar panels would
need to convert approximately 50% of the light striking them to
electricity.(This is much higher than
current production solar panels can do, but the technology is under development
and in the lab has reached 42%.)The daughter
craft would use very small ion (“electrospray”) engines to set up their
encounters with the moons.The craft
would need to be able to carefully manage their power use and storage and
largely operate autonomously.

Abtract 1291: Mars Aerial Vehicle – Airplanes have been proposed for
Martian exploration since at least the late 1970s.The extremely thin atmosphere of Mars makes
flight difficult, and the proposals I recall all had lives measured in hours
before they exhausted their power reserves and crashed.This proposal would make the craft part
balloon and part aircraft.The shape
would be that of an aircraft, but the body and winds would be filled with
helium, giving the craft 70% neutral buoyancy.The rest of the necessary lift would come from a propeller powered by
batteries that would be recharged by solar cells on the wings.While the abstract doesn’t discuss how long
the craft might operate, it would seem that it could operate for at least days
and perhaps much longer until too much helium had leaked out.The aircraft would carry a ground penetrating
radar and a magnetometer to search subsurface ice and hydrated soils.Because the aircraft would be much closer to
the surface than orbital spacecraft, resolution would be much higher, allowing
it to pinpoint local deposits.

Several instruments that would date Mars material could measure dates
for a diversity of rock and soil fragments within a sample.This image shows the laser operating in a
grid pattern. Note that each sample is a
small fraction of a square millimeter. From LSPC 2013 Abstract 1762.

Abstract 1762: Rb-SrDating –
Over the last few years, several research teams have made good progress in
developing instruments that could date rocks and soils and be carried on Mars
rovers.Unlike most worlds whose rocks
formed within a few hundred million years of the birth of the solar system,
Martian rocks have formed over billions of years.Unfortunately, establishing the chronology of
Mars’ geologic history has been tough and subject to large errors.(The current method depends on counting
craters, with surfaces that are older having more craters.However, the rate at which craters are formed
is uncertain and craters on Mars can be buried by dust or eroded away.)The instruments under development would
examine rocks on Mars and fix their age to within tens of millions of
years.Most of the instruments, such as
the one described in this abstract, would use micro lasers to melt tiny (~75x5
microns in this case) samples of rock or soil.The instruments would then measure the ratios of key isotopes in the
released vapor to establish ages.One
of the elements would be the radioactive decay product of the other; since the
rate of decay is well known, the ratio of the two would establish the age.This abstract is one of several at the LPSC
meeting describing progress.I’ve
highlighted this one because it is more descriptive (i.e., less technical) than
the others and probably would be the most readable for many of the readers of
this blog.Editorial Note: The next
opportunity for one of these instruments to fly to Mars would be on NASA’s 2020
rover.I don’t know if any will be
technically ready in time or whether the limited instrument budget for that
mission can afford the cost of completing development for a flight ready
instrument.

Tuesday, March 12, 2013

By July 1, a group of scientists will define the goals of the rover
NASA will launch in 2020 to Mars. The
rover will be a near twin of the Curiosity rover that is currently on
Mars. (Since Curiosity is nuclear
powered, it may still be operating when its sibling arrives.) The Curiosity design will ensure that the
rover is highly capable. What the
Science Definition Team (SDT) will determine is what its scientific goals
are. From those goals, NASA will select
a suite of instruments to fulfill those goals.

What I’ll attempt to do in today’s post is to discuss some of the
tradeoffs that I think may be considered in selecting the science goals. I won’t attempt to discuss potential
individual instrument selections – the scientific community is tremendously
creative in developing instrument concepts, many of which lie outside my
expertise.

The most basic question will be whether to do detailed composition analysis there, here, or both. There means on the surface of Mars, and here means returning samples to the
laboratories of Earth. The Phoenix
lander, Curiosity rover, and the planned European and Russian 2018 ExoMars
rover will carry highly sophisticated chemical laboratories rovers
(science there). However, while the instruments on those rovers are
engineering marvels, they are pale imitations of the incredibly more varied and
sensitive instruments in laboratories here on Earth (science here).

The Mars community has decided (formally through the last Decadal
Survey) that answering the key questions about Mars requires the sophistication
of Earth-based instruments. The goal
identified in the Survey for the next Mars rover was to find and cache samples
for eventual return to Earth. Science
instruments on the rover would serve primarily to identify interesting samples
to collect. The catch, though, is that
returning those samples will require two additional missions costing
$4-6B. In an era of shrinking US federal
budgets, any samples collected may languish on Mars for a decade, perhaps several,
and possibly forever

In a world of plush budgets, focusing the 2020 rover on simple sample
collection would be the obvious choice (as it was for the members of the
Decadal Survey in days of rosier budget forecasts). In a world of shrinking US Federal budgets,
though, the SDT members may decide that equipping the rover with highly capable
– but expensive ($10s of millions) – instruments may be a better choice. With this strategy, whether samples are
returned or not, the rover will have conducted sophisticated analyses of rocks
and soils: A guaranteed science return.

So why not just do both? Collect
samples and carry a sophisticated science laboratory? The answer is a limited budget and
conflicting operational strategies. The
former is simpler to explain. The science
instrumentation budget for the 2020 rover is expected to be $80-100M,
approximately half that available for developing the Curiosity rover’s
instruments. NASA’s managers have stated
that the budget won’t provide the funds for developing a full suite of complex
new instruments.

The conflict in the operational strategies arises from how to maximize
the use of time. (While the 2020 rover
may operate for many years, planners can count on only the two it is designed
for.) For a caching-focused mission, the
goal is to visit as many locations as possible, assess their potential for
samples worthy of return to Earth, and move on quickly from the many that don’t
make the cut. For a science on
Mars-focused mission, the preparation and analysis of each sample requires long
periods parked in one spot. (Think of
the weeks Curiosity has spent parked in each of the two locations it has
analyzed samples (although the process should speed up as the rover’s operators
gain experience).)

For either mission strategy, two sets of instruments might be the
same. The first suite will consist of
remote sensing instruments that study the surrounding landscape without
physically touching any of it. Cameras
will serve as the eyes of geologists (and armchair explorers on Earth). The rover may carry one or more spectrometers
that analyze different portions of the electromagnetic spectrum to map
composition. The Spirit, Opportunity,
and the ExoMars rover used or will use this approach. An alternative would be to use a laser to vaporize
rock and soil surfaces to enable chemical analysis of the briefly glowing vapor
as the Curiosity rover does. Whatever
the instruments selected, their goal will be to select specific locations for
study or sampling and to understand the geological context.

A second set of instruments would be located on the rover’s arm and
would be physically placed in contact with soils and rocks to make their
measurements. The Spirit, Opportunity,
and Curiosity rovers carried both microscopic imagers and spectrometers to
measure composition. (The ExoMars rover
will not have a robotic arm and doesn't have equivalent instruments, although
it will have an infrared spectrometer embedded in its drill bit.) The advantage
of these instruments is that they conduct their measurements quickly, allowing
fast assessments. The downside is that
the types of instruments and their sophistication are limited by the need to
fit on the head of the robotic arm and be exposed to the harsh Martian
environment.

For the 2020 rover, though, the compositional contact instruments may
be much more sophisticated than those flown to date. Previous instruments measured average
composition across each sample area (1.7 cm for Curiosity). If you look closely at soils and most rocks,
you’ll see that they are composed of many smaller rock fragments, each with its
own story. The next generation contact
images may be able to differences composition across the contact area as small
as 0.5 mm or smaller.

Regardless of the science focus, the 2020 rover seems likely to carry
instruments from these first two suites.
Depending on the science goals, it may also carry a third suite, an
analytical laboratory. These would be
instruments within or mounted on the rover that receive samples delivered by the
rover’s drill or scoop. These
instruments can be larger, allowing for more sophisticated measurements. They can also manipulate the samples, say
heating them to drive off organic molecules or wetting them to measure the
resulting chemical reactions. The Spirit
and Opportunity rovers were too small to carry these instruments, but Curiosity
carries two. The Phoenix lander also had
an analytic laboratory as will the ExoMars rover.

The range of instruments possible for an analytical laboratory is wide,
and I seem to find two or three new proposals with each scientific conference
that includes discussions of future Mars missions. One core instrument type is a mass
spectrometer and gas chromatograph combination that can “taste” gases driven
off a sample by heating a sample. This
is a standard technique for measuring carbon chemistry, including organic
molecules. The Curiosity rover carries
one (the Sample Analysis at Mars, or SAM instrument) and the ExoMars rover will
carry a more capable version.

An exciting new class of instruments that are maturing to become flight
ready would perform geochronology on Mars rocks and soils to nail down their
ages. Understanding the age of key events
in Mars’ history, recorded in its rocks and soils, is one of the motivating
goals of returning samples to Earth. The
development of instruments that can be carried to Mars provides an opportunity
to address key questions without the cost of returning samples.

However, NASA’s managers have already stated that the limited
instrument budget for the 2020 rover will preclude development of a suite of
new instruments. That would seem to
favor the remote sensing and contact instruments over the more capable but also
much more complex and expensive laboratory instruments. A previous science definition team that
examined instruments for a caching rover called for only remote sensing and
contact instruments.

Careful ‘shopping’, though, may be able to extend the budget. NASA could fly copies of the Curiosity
instruments, whose development has already been paid for. It might also fly copies of one or more of
the ExoMars instruments. (The ExoMars
MOMA instrument itself uses a copy of much of the Curiosity’s SAM
instrument.) NASA has also said it is open
to instruments provided by – and very importantly, paid for – by other nations.

Editorial Thoughts: I have seen a multitude of proposals for Mars
sample return over the past several decades and not one has come close to being
funded. I personally am wary of flying
a rover mission that focuses too heavily on sample acquisition and
caching. Those samples may never reach
Earth, and funds for major rover missions may come very infrequently. While planetary scientists see sample return
as the necessary next step, the long history of failed sample return proposals
suggests that returning rocks exciting to geologists and astrobiologists
doesn’t open the public checkbook for a many billion dollar outlay. (My personal guess is that Congress will
provide the funds for a sample return if a rover finds complex organic
molecules suggesting past or present life. )

I will be shocked if the SDT doesn’t call for the rover to collect and
cache samples in case governments come to feel generous. However, I’d also like to see one or more
complex analytical instruments fly, even if they are copies of previously flown
instruments. So do science there and enable science here.
That would guarantee more sophisticated measurements, and the
measurements they do make may show that the samples exciting to the general
public as well as scientists.

About Me

You can contact me at futureplanets1@gmail.com with any questions or comments.
I have followed planetary exploration since I opened my newspaper in 1976 and saw the first photo from the surface of Mars. The challenges of conceiving and designing planetary missions has always fascinated me. I don't have any formal tie to NASA or planetary exploration (although I use data from NASA's Earth science missions in my professional work as an ecologist).
Corrections and additions always welcome.